Biomarkers for Niemann-pick C disease and related disorders

Abstract

Methods for screening or diagnosing subjects for disorders involving accumulation of one or more oxysterols such as cytotoxic oxysterol accumulation, Niemann-Pick C(NPC) disease, lysosomal storage diseases, cholesterol trafficking diseases, and neurodegenerative diseases. Also provided are methods for methods for screening or diagnosing subjects (including infants and neonatal subjects) for NPC disease, methods for monitoring the progression, remission, and clinical status of NPC disease, and methods for evaluating the efficacy of therapeutic treatment of NPC disease.

What is claimed is: 
     
       1. A method for determining whether a subject suspected of having Niemann-Pick C disease is afflicted with Niemann-Pick C disease, the method comprising:
 (a) obtaining a body fluid sample from the subject; 
 (b) subjecting the sample to a chromatography-mass spectroscopy analysis to determine the concentration in the sample of at least one oxysterol selected from the group consisting of 7-ketocholesterol and cholestane-3β, 5α, 6β-triol; 
 (c) comparing the concentration of the at least one oxysterol present in the sample to a reference value of the at least one oxysterol obtained from a control population consisting of individuals not afflicted with Niemann-Pick C disease; and 
 (d) diagnosing the subject as afflicted with Niemann-Pick C disease if the concentration of the at least one oxysterol from the subject is greater than the reference value. 
 
     
     
       2. The method according to  claim 1 , wherein determining the concentration of the at least one oxysterol comprises:
 (a) adding a known amount of an oxysterol internal standard to the body fluid sample; 
 (b) extracting the at least one oxysterol from the body fluid sample; and 
 (c) quantifying the extracted at least one oxysterol using a chromatography procedure. 
 
     
     
       3. The method of  claim 1  wherein the control population comprises individuals not afflicted with Niemann-Pick C disease matched with the subject in either one or both of age and sex. 
     
     
       4. The method of  claim 3 , wherein the reference value is an average oxysterol concentration of a non-Niemarm-Pick C afflicted control group. 
     
     
       5. The method of  claim 1 , wherein the subject is identified as afflicted with Niemann-Pick C disease when the concentration of the at least one oxysterol in the subject body fluid sample is more than about 2 fold greater than the reference value, and wherein the reference value is an average oxysterol concentration in the same body fluid sample type from a healthy control population matched with the subject in at least one of sex or age. 
     
     
       6. A method for determining whether subject is afflicted with Niemann-Pick C disease in accordance with  claim 1 , wherein the subject is a neonatal subject and the control population is a neonatal control population. 
     
     
       7. The method according to  claim 6 , wherein the determining the concentration of the at least one oxysterol comprises:
 (a) providing a neonatal screening card spotted with the body fluid sample from the neonatal subject; 
 (b) spotting to the neonatal screening card a known amount of an oxysterol internal standard; 
 (c) extracting the at least one oxysterol and the oxysterol internal standard from the neonatal screening card; and 
 (d) determining the concentrations of the extracted at least one oxysterol and the internal standard using a chromatography procedure. 
 
     
     
       8. The method of  claim 6 , wherein the reference value is an average oxysterol concentration of an a non-Niemann-Pick C afflicted control group. 
     
     
       9. The method of  claim 6 , wherein the neonatal subject is identified as afflicted with Niemann-Pick C disease when the concentration of oxysterol in the subject body fluid sample is more than about 2 fold higher than the average oxysterol concentration found in the same body fluid sample from sex-matched controls of non-NPC afflicted neonates. 
     
     
       10. The method of  claim 1 , wherein the body fluid is selected from the group consisting of plasma, serum, blood, sputum and amniotic fluid. 
     
     
       11. The method of  claim 1 , wherein the body fluid is selected from the group consisting of plasma, serum and blood. 
     
     
       12. The method of  claim 1 , wherein the body fluid is plasma. 
     
     
       13. The method of  claim 10 , wherein the blood is cord blood. 
     
     
       14. A method for determining the status of Niemann-Pick C disease in a subject with Niemann-Pick C disease, the method comprising:
 (a) obtaining at least one body fluid sample from the subject; 
 (b) quantifying at least one oxysterol selected from the group consisting of 24-hydroxycholesterol, 7-ketocholesterol, cholestane-3β, 5α, 6β-triol, and a combination thereof, in the body fluid sample to determine a quantification value; 
 (c) determining the magnitude of the difference between the quantification value and a reference value of the same at least one oxysterol obtained from the subject at an earlier time or from a control population consisting of individuals not afflicted with Niemann-Pick C disease, thereby identifying the status of Niemann-Pick C disease in the subject. 
 
     
     
       15. The method of  claim 14  wherein the quantification value comprises the concentration of 7-ketocholesterol, cholestane-3β, 5α, 6β-triol, or both, whereby if the concentration of 7-ketocholesterol, cholestane-3β, 5α, 6β-triol, or both, is greater than the reference value, then the subject is not deemed to exhibit remission of the Niemann-Pick C disease. 
     
     
       16. The method according to  claim 14 , wherein quantifying the at least one oxysterol comprises:
 (a) adding a known amount of an oxysterol internal standard to the body fluid sample; 
 (b) extracting the at least one oxysterol from the body fluid sample; and 
 (c) quantifying the extracted at least one oxysterol using a chromatography procedure. 
 
     
     
       17. The method according to  claim 16 , wherein the quantifying the extracted at least one oxysterol comprises:
 determining area under the curve for the oxysterol internal standard; 
 determining area under the curve for the at least one oxysterol; and 
 comparing the area under the curve obtained for the known amount of oxysterol internal standard with the area under the curve obtained for the at least one oxysterol. 
 
     
     
       18. The method of  claim 14  wherein the quantification value of the at least one oxysterol comprises the concentration of 24-hydroxycholesterol, whereby an increase or stabilization of 24-HC levels indicates remission of Niemann-Pick C disease in the subject.